HP 15C memory


Hi I lost the manual of my HP 15C calculator. I can't store in memory 2,3,.. memory 1 is OK. I get error 3. Also X-av. and s , sigma -, sigma+ don't work. Anybody can help? Thanks


(Moderator repost from HP Articles Forum)


If you want to use till R7 (ie:for statistics) do: 7 DIM (i)



this is just to add a bit more info to Rauls precise answer.

if you want to start from the default, you can do what Raul sugests with 19 instead of 7, say,

19 [f] [DIM] [(i)]
The default number of initial available registers for the HP15C is 20, i.e., R0 to R19. R0 and R1 are always available, because they are needed to address matrix elements (R0-row#, R1-column#)



And, if you want to make sure that all memory is clear (be careful - you'll loose all program and register contents), just turn it on while holding '-' (minus) key.


Ahhh, this must be because the 15C keeps a "pool" of unallocated registers. I'd thought it was a "sliding curtain" between memories and program steps, but then where would storage for matrices go? Thanks, I better understand this myself now.

Does anybody know if this was the first such HP calc to have "unallocated memory"?



Hi, Glen;

the HP15C is the only Voyager able to do that. You can "define" a "partition" with (N+1) registers, provided that N is in X-register as you execute [f][DIM][(i)]. The other (65-N) registers are for:

Imaginary part of the complex stack, if complex mode is activated: 5 registers
SOLVER: 5 registers
INTEGRATION: 23 registers
MATRIX elements, one register for each defined element

The only exception is when you use SOLVE with INTEGRATION at the same time, what needs 23 registers and not 28, as expected. The maximum available registers for a minimun register number (N=1 is minumun, even if you try 0 [f][DIM][(i)]) is 64, what gives you enough space to store an 8X8 matrix.

Before the HP15C the only calcualtor that allowed this sort of user controlled partition was... guess? Yes, the old HP41.

Cheers and best regards, my friend.


Thank you, friend Luiz. Yeah, it figures (so to speak), the 41 community seems the biggest here, and the 15 & 42 are the most popular shirt-pockets.... These are all three _very_ good calculators.


Yes, as mentioned, the 42S can do the same. After a memory clear, it defaults R00 to R24 as storage registers. You can enlarge this to a maximum of available memory with [shift] [mode] [\/] [SIZE] [number] [enter], Where [number] is the number of registers you want. Anything beyond R99, you must use indirect addressing.

Makes a 15C memory space seem small when it reports 6977 bytes free, or if you've installed 32k, 31533 bytes free. One can never have enough free memory...



I was wondering about the subject (thanks, Glen) and I can only remember these three "amigos" (in order of appearance: HP41, HP15C and HP42S) as the only ones with user-defined "allocatable" memory.

Is there any other HP that does this "trick"? All of the other Pioneers are one of both: financial or less-powerful scientific. All other scientifics after the HP42 (28, 48, 49) have automatic allocation and work with objects, not numbered registers.

Am I missing someone? Any vintage? I read something very peculiar about the HP95C program memory, but its registers segment has a fixed number of registers, right?

As I am always curious bout this sort of subject, this is another "Just curiosity.".



Thanks. The problem is solved.

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